The goals of this research are fourfold: 1) to carry out experiments to determine the effects of chronic administration of delta 9-THC and other marihuana constituents on the cardiovascular system; 2) to compare the effect of delta 9-THC in anesthetized and conscious animals; 3) to study the effect of delta 9-THC on experimental models of cardiovascular diseases and interaction of these agents with certain commonly used cardiovascular drugs, 4) to determine the mechanisms underlying the effects observed and evaluate toxicity of marihuana. Physiological experiments will be conducted to measure changes in cardiac output, left atrial and ventricular pressures and peripheral vascular resistance. Direct effects on vasculature and myocardium will be distinguished from central and autonomically mediated effects. Ventricular function will be assessed in the treated dogs during resting conditions and during external stress such as exercise. Biochemical studies will be conducted to correlate changes in central and peripheral cholinergic and monoaminergic mechanisms to the observed hemodynamic alterations. Other studies will include monitoring of plasma steroid level correlates with the autonomic and cardiovascular effects.